Energy Efficient Heat Sink Design: Natural Versus Forced Convection Cooling

In highly efficient converter systems, the power consumption of the cooling system (fans) significantly influences the total system efficiency as well as the power density. This paper investigates the potential of free convection cooled heat sinks and compares their performance to forced convection cooled heat sinks on the basis of their volume and power consumption. Underlying theoretical concepts for both types of cooling systems are summarized and their application in an optimization procedure is presented. The theoretical concepts are validated with prototype heat sinks. Finally, at an example of a half-bridge converter, it is shown that by free convection cooling, not only the efficiency but also the power density can be increased. In this case, by paralleling semiconductor devices the losses decrease approximately by a factor of three while simultaneously the heat sink volume can be reduced by approximately 50%.